Cellular radio communications systems are increasingly employed to provide wireless voice and data communications to a number of mobile units or subscribers. Cellular radio communications systems include both analog cellular systems, such as the "AMPS" system, and, more recently, digital cellular systems, such as the pan-European "GSM" system. These systems, and others, are described in a book entitled Dual Mode Cellular by Harte, published by P. T. Steiner Publishing Co., Bridgeville, Pa. (1992).
A cellular radio communications system generally includes one or more cellular telephones, one or more radio base stations and a Mobile Telephone Switching Center (MSC). A typical cellular radio communications system can include hundreds of radio base stations, thousands of cellular telephones and one or more MSC's. A cellular radio communications system includes a number of spaced apart radio zones referred to as cells. Each cell includes a radio base station for transmitting and receiving messages to and from cellular telephones which are located within the cell range.
Each cell of the cellular radio communications system typically includes a plurality of duplex voice channels over which cellular telephone messages are carried. Each cell is also provided with a number of control channels to control the operation of the cellular telephones and the assigned voice channels. Accordingly, through the cellular radio communications system, a duplex radio communication signal or link can be established between two cellular telephones or, between the cellular telephone and the wire line telephone.
As used herein, the term "cellular telephone" encompasses a wide variety of portable telephone devices which access a cellular radio communications system. Cellular telephones include mobile telephones that are hand held or of a bag phone variety and permanently mounted car cellular telephones. The term "cellular telephone" also include terminals which provide functions in addition to those of a cellular telephone, such as facsimile, data communications, data processing, word processing applications and other personal communication systems functions. These highly functional cellular telephones are often referred to as "Personal Communication Systems."
Each radio base station generally includes a control unit and an associated antenna. With respect to the cellular telephones located within the cell range, the base station functions chiefly to relay messages to and from the cellular telephones. The radio base station also supervises the quality of the communications link with the cellular telephones. A typical radio base station is Model No. RBS882 manufactured by Ericsson Telecom AB Stockholm, Sweden for the CMS8800 cellular mobile telephone system. A full description of this analog cellular network is provided in Publication No. EN/LZT 101 908 R2B, published by Ericsson Telecom AB.
A number of base stations are connected to a single MSC which acts as the central coordinating element of the cellular system. The MSC includes a cellular processor and a cellular switch connected to the Public Switched Telephone Network (PSTN) to allow communications between the cellular telephones and wire line telephones. The MSC can also be associated with a Home Location Register (HLR). The HLR includes storage means for storing data relating to the subscribers of the cellular system. This data can include the telephone number of the subscriber as well as any specific services requested by the subscriber, such as call waiting or call hold. The HLR can also include processing means for manipulating the stored subscriber data.
A feature node can also be associated with the MSC of a cellular radio communications system or with another associated communications network, such as the PSTN. For example, the feature node can be incorporated within or associated with the HLR. Even if the feature node is associated with another communications network, such as the PSTN, the cellular radio communications network can access the feature node via the interconnection between the MSC of the cellular radio communications system and the PSTN or other communications network.
A feature node provides predetermined functions to the cellular telephones or the telephones associated with the PSTN, such as, for example, establishing an efficient communications link between telephones, such as via intermediate radio base stations, or providing voice-controlled speech information and number translation services as well as facilitating the establishment of conference telephone calls. Still further, a feature node can provide paging services for the user of a cellular telephone and can facilitate the establishment of alternative communications links if the primary communications link is unavailable. A feature node is described, for example, in more detail in U.S. patent application Ser. No. 018,268 entitled "A Method Of Establishing Cooperation With A Functionality" and U.S. patent Application Ser. No. 018,223 entitled "A Method 0f Organizing Communication", both of which were filed on Feb. 16, 1993 and both of which are incorporated herein by reference.
Numerous subscribers or users of a cellular radio communications system have more than one telephone, each of which is typically assigned a different telephone number. For example, cellular radio communications system subscribers typically have a telephone at their place of business (hereinafter referred to as a "work telephone"), a telephone at their residence (hereinafter referred to as a "home telephone") and a cellular telephone. In order to provide parties with the best opportunity to contact the subscriber, the subscriber must generally provide the calling party with the telephone number assigned to each of the different telephones associated with the subscriber. For a subscriber having several telephones, it is undesirable to provide another party with each of the telephone numbers due to the sizeable amount of information which must be accurately exchanged between the subscriber and the calling party. Further, the calling party must record and retain not just one telephone number, but several telephone numbers associated with the subscriber.
Even if each telephone number associated with the subscriber is accurately provided to and recorded by the calling party, the calling party can generally only place a telephone call to the telephone number assigned to one of the subscriber's telephones at a time. Thus, the calling party typically places an initial call to the telephone at which the calling party believes the subscriber is most likely to respond. If the subscriber does not respond to the alert of the telephone which was initially called, the calling party must subsequently try one or more of the remaining telephone numbers assigned to other telephones associated with the subscriber. Accordingly, the calling party must typically place several different telephone calls, each of which require the entry of a different telephone number, in an attempt to reach the subscriber. This process of placing a telephone call to a subscriber is thus not only laborious for the calling party, but is also prone to errors in the recordation and entry of the telephone numbers.
Each telephone call placed to or from a cellular telephone increases the load on the cellular radio communications system with which the cellular telephone is associated. Based upon the components of cellular radio communications system, each system typically has a predetermined maximum allowable load which it is adapted to efficiently accommodate. The operators of the cellular radio communications system, however, do not generally charge a fee for unanswered telephone calls even though such calls increase the system's load. Therefore, the multiple telephone calls which can be placed in an attempt to reach a subscriber who is associated with a plurality of telephones increase the load of the cellular radio communications system without allowing the operator of the cellular radio communications network to charge a fee. Thus, there is a need to provide methods and systems to allow a calling party to efficiently place a call to a subscriber of a cellular radio communications system who is associated with several telephones, each of which has a different telephone number.